A semiconductor light-emitting device such as a light-emitting diode (LED) or a laser diode (LD) uses an electroluminescence phenomenon whereby light is emitted from a material (semiconductor) by supplying current or applying voltage. While electrons and holes are combined with each other in an active layer (for example, an emissive layer) of the semiconductor light-emitting device, energy corresponding to an energy band gap of the active layer may be emitted in the form of light. Thus, according to the size of the band gap of the active layer, a wavelength of the light emitted from the semiconductor light-emitting device may vary.
A semiconductor light-emitting device may be classified into a two-dimensional (2D) light-emitting device (which is a thin film-type light-emitting device) including a 2D active layer and a three-dimensional (3D) light-emitting device including a 3D active layer.
In a light-emitting device including a 3D light-emitting device, for example, a plurality of nanorod structures, an active layer is formed in a 3D form. Compared with a 2D light-emitting device, the 3D light-emitting device may have an increased light-emitting area to increase a luminous efficiency. In addition, it is relatively easy to freely select colors that are realized by the 3D light-emitting device.
However, although a light-emitting area of a 3D light-emitting device is increased, a luminous efficiency is not increased by as much as the increase in the light-emitting area. Since light that is emitted upward or downward in a 3D light-emitting device is transmitted through a relatively short optical path of a light-absorbing member, such as a transparent electrode, light absorption is relatively low. However, since light that is emitted in a lateral direction, is transmitted through a very long optical path, light absorption is relatively high.
Accordingly, there exists a need for further improvements in light-emitting devices which minimize the number of times that light is transmitted through a light-absorbing member in order to increase luminous efficiency of the device.